import java.util.HashSet;
import java.util.Set;

public class BUG {
    public static void main(String[] args) {
      Set<String> set = new HashSet<String>();
        set.add("one");
        set.add("two");
        Set<Set<String>> setOfSets = new HashSet<Set<String>>();
        setOfSets.add(set);
        boolean found = setOfSets.contains(set); // returns true
        set.add("three");
        Set<Set<String>> newSetOfSets = new HashSet<Set<String>>(setOfSets);
        found = setOfSets.contains(set); // returns false
      System.out.println(found);
        found = newSetOfSets.contains(set); // returns true

    }
}
